Method of and Apparatus for Manufacturing a Metal Strip

ABSTRACT

The invention relates to a method for manufacturing a metal strip ( 1 ), in which the metal strip ( 1 ) is guided over a number of rolls ( 2, 3, 4, 5 ) under such a strip stress (S), and is moved in a conveying direction (F), that it is largely flat at least between two rolls ( 2, 3 ). In order for it to be possible to inspect the strip in a simple and space-saving way, the invention provides for the inner tensile stresses which act in the metal strip ( 1 ) which is largely flat under tensile stress between the at least two rolls ( 2, 3 ), to be made optically visible and for the tensile stresses or tensile stress differences which are determined in this way to be utilized during the manufacture of the metal strip ( 1 ). Furthermore, the invention relates to an apparatus for manufacturing a metal strip.

The invention relates to a method of manufacturing a metal strip inwhich the metal strip is guided over a number of rolls under such striptension and is advanced in a transporting direction so that it is flatto a large extent at least between two rolls. The invention furtherrelates to an apparatus for manufacturing a metal strip.

During rolling and skinpass rolling of a metal strip, the flatness,together with the thickness and cleanliness of the strip, is a decisivefactor. Therefore, it is necessary to undertake inspection duringmanufacturing of a metal strip to insure quality of the production,wherein, if necessary, based on the results produced by inspection, themanufacturing process should be modified.

To the end, in conclusion of a rolling process, often, the metal stripis subjected to the flatness measurement, wherein unevenesses of thestrip should be revealed. To this end, flatness measuring rollers areused which are pressed with a predetermined prestress against a metalstrip that is guided under tension. By measuring the imprints of theflatness measuring roller resulting from the unevenesses of the metalstrip, a conclusion can be made about the unevenesses in the metalstrip. Also known are systems that visualize differences in tensioncaused by its variations.

Unevenesses in a metal strip can be determined not only with contactingrollers but also in contactless manner. To this end, e.g., the JP2000046752 A discloses an optical system that has an illuminating devicefor the strip and cameras. Therefore, it is possible tothree-dimensionally measure the surface of a metal strip and determinedthe measurement result.

Flatness of a metal strip can also be measured with an apparatus such asdisclosed in EP 1 418 400 A2. Here, likewise, deviations are determinedwith a camera (CCD-Kamera: Charge-Coupled-device camera).

Similar systems are disclosed in DE 197 58 466 A1 and DE 199 32 324 A1.

In all of the above-mentioned cases, unevenesses of the strip surfaceare measured and, if necessary, change of process parameters isundertaken.

It has been determined that specific measurement results under acorresponding strip tension are difficult to interpret because,dependent on the strip tension that is applied to the metal strip,flatness changes. Therefore, based on the strip tension to which arolling stock is subjected in a rolling process, the stress differencesover the strip width in form of buckling or unevenesses cannot berecognized or are recognizable with much difficulty.

It is particularly desirable to be able to visualize the stressdistribution over the width of the metal strip in order to make aconclusion about the strip quality. At that, the apparatus for thisdetermination should be formed in a space-saving manner and should notrequire any large expenses for its installation and operation.

Accordingly, the object of the invention is a method and an associatedapparatus of the type discussed above modified so that it is possible toobtain information even under a high strip tension which would enable tocontrol the manufacturing process in such a way that the strip qualityis optimized.

This object is achieved according to the invention by a method accordingto which in the metal strip, which is flat to a large extent undertension between the at least two rolls, inner tensile stresses are madeoptically visible, and the generated tensile stresses or tensile stressdifferences are used during manufacturing of the metal strip.

According to an improvement, a strip tension applied to the metal stripis selected dependent of the tensile stresses generated in the metalstrip.

Advantageously, it is contemplated that with an increased tensile stressin the metal strip, the strip tension, which is applied to the metalstrip is also increased.

By the input of the associate high or low individual tension into thecontrol circuit, the flatness can be influenced.

Advantageously, the metal strip is illuminated with a light source andis photographed with two cameras from two different directions.

Tensile stresses, which act in the metal strip, which can be determinedby the above-mentioned process, advantageously, are determined multipletimes with short time intervals. The change of the tensile stresses,which act in the metal strip, can be ascertained by comparison of anumber of tensile stresses determined in time intervals. With aplurality of pictures following one another within a short time, stresspictures for a rapidly moving strip are obtained.

The device for manufacturing a metal strip includes a number of rollsover which a metal strip is guided under a such strip tension and isadvanced in a transporting direction so that it is flat to a largeextent at least between two rolls.

According to the invention, it is provided that between two rollers, atleast one light source for illuminating the metal strip is arranged, andin the region of the light source, at least one, preferably two, camerasis or are arranged and which take(s) pictures of the illuminated metalstrip, and wherein the system consisting of a light source and camera orcameras is suitable for revealing tensile stresses acting in the metalstrip.

Advantageously, two cameras are available which are arranged at adistance from one another so that the metal strip is photographed fromtwo different directions. The cameras are preferably digital.

Further, receiving means, which stores the pictures taken by the cameraor cameras in short time intervals, are available.

Finally, it is provided that the receiving means is connected withevaluation means suitable for comparison of pictures taken by the cameraor cameras.

With the proposed process it is possible to guide the metal strip undera relatively high tension after rolling and thereby to a large extentflatly and, despite that, to be able to determine the unevenness of thestrip, without taking into account high tensile stresses in the strip.The determined tensile stresses give a good indication of the quality ofthe finished strip so that, if necessary, the manufacturing parameterscan be influenced.

Further features and particularities of the invention follow from theclaims and the description of an embodiment of the invention shown inthe drawing. The single drawing shows a side view of a rolling apparatusfor manufacturing metal strips.

A metal strip 1 is rolled in the left region of the figure in a rollingregion by working rolls 11 and 12 which are supported by two back-uprollers 13 and 14. Then, the metal strip 1 is advanced in a transportingdirection F with a predetermined transporting speed, while being held ata certain strip tension S. The strip tension S is maintained by guidingthe metal strip 1 linearly. It is guided, as it is particularly shown atthe right side of the figure, by two rollers 4 and 5 in a S-shapedmanner, so that a desired level of the strip tension S can be maintainedbetween rolls 11, 12 and rolls 4, 5.

Due to the strip tension S, the metal strip 1 has a high degree offlatness, i.e., the surface unevenness is small.

Between two rolls 2 and 3, the metal strip 1 is guided flatly to a largeextent. There, a light source 6 is arranged that illuminates the surfaceof the metal strip 1. Further, two cameras 7 and 8 are provided at twodifferent locations and an take two pictures of the strip surface.

The system that consists of the light source 6 and cameras 7 and 8 andthat is suitable for the inventive method is known under Q-400 mark asdigital 3D-Correlation System of the firm DANTEC Ettemeyer GmbH,Elchingen, Germany (www.dantec-ettemeyer.com) and can be obtained fromthe firm. The available system is suited very well for revealing innertensile stresses in the, to a large extent flat, metal strip and fortheir evaluation even when strip tension variations in a small numberare necessary.

The cameras 7 and 8 is connected with receiving means 9 that is capableof storing a number of pictures in a short time. The taken pictures canbe evaluated by adjoining evaluation means 10, which permits to observedistribution of tensile stresses in the metal strip and their variationwith time. Dependent thereon, the manufacturing process of the metalstrip 1 can be regulated.

Advantageously, during the measurement of the stresses, the striptension that corresponds to at least 10% of the limit of elasticity ofthe material of the metal strip, is maintained.

The use of the revealed tensile stresses or tensile stress differencesin the metal strip 1 during the manufacturing of the metal strip 1 canconsist in that the tensile stresses in the strip are observed and onlywhen needed, i.e., when the stress distribution proportions in the stripexceeds an unallowable value, certain measures are undertaken.

However, a case can be contemplated when the generated values are inputinto a closed control circuit that directly controls the manufacturingprocess of the metal strip.

REFERENCE NUMERALS

-   -   1. Metal Strip    -   2. Roll    -   3. Roll    -   4. Roll    -   5. Roll    -   7. Camera    -   8. Camera    -   9. Receiving Means    -   10. Evaluation Means    -   11. Working roll    -   12. Working roll    -   13. Back-up roll    -   14. Back-up roll    -   S Strip tension    -   F Transportation direction

1. A method of manufacturing a metal strip (1) in which the metal strip(1) is guided over a number of rolls (2, 3, 4, 5) under a such striptension (S) and is advanced in a transporting direction so that it isflat to a large extent at least between two rolls (2, 3), wherein in themetal strip (1), which is flat to a large extent under tension betweenthe at least two rolls (2, 3), inner tensile stresses are made opticallyvisible, and the generated tensile stresses or tensile stressdifferences are used during manufacturing of the metal strip (1),characterized in that the metal strip (1) is illuminated with a lightsource (6) and is photographed with cameras (7, 8) from two differentdirections.
 2. A method according to claim 1, characterized in that astrip tension (S) applied to the metal strip (1) is selected dependentof the tensile stresses generated in the metal strip (1).
 3. A methodaccording to claim 2, characterized in that with an increased tensilestress in the metal strip (1), the strip tension (S), which is appliedto the metal strip (1) is also increased.
 4. (canceled)
 5. A methodaccording to claim 1, characterized in that the tensile stresses, whichact in the metal strip (1), are determined multiple times in short timeintervals.
 6. A method according to claim 5, characterized in that thechange of tensile stresses acting in the metal strip (1), is effected bycomparison of a number of tensile stresses produced in time intervals.7. An apparatus for manufacturing a metal strip (1) in which the metalstrip (1) is guided over a number of rolls (2, 3, 4, 5) under a suchstrip tension (S) and is advanced in a transporting direction that it isflat to a large extent at least between two rolls (2, 3), characterizedin that between two rollers (2, 3), at least one light source (6) forilluminating the metal strip (1) is arranged, and in the region of thelight source (6), two cameras (7, 8) are arranged and which takepictures of the illuminated metal strip (1), wherein the systemconsisting of a light source (6) and cameras (7, 8) is suitable forrevealing tensile stresses acting in the metal strip (1), wherein thetwo cameras (7, 8) are arranged at a distance from one another so thatthe metal strip (1) is photographed from two different directions. 8.(canceled)
 9. An apparatus according to claim 6, characterized in thatreceiving means (9) is available that stores the pictures taken by acamera or cameras (7, 8) in short time intervals.
 10. An apparatusaccording to claim 1, characterized in that the receiving means (9) isconnected with evaluation means (10) suitable for comparison of picturestaken by the camera or cameras (7, 8).